Field of the Invention
The present invention relates to a communication apparatus and a method for controlling the communication apparatus.
Description of the Related Art
Conventionally, in the case where data is read out from a memory card such as an SD memory card, the delay amount of data transmission from the card relative to a clock provided to the card from a host was a standardized fixed value. Accordingly, the host side was able to access the card without issue, by latching data at a timing delayed by the standardized amount relative to the clock transmission.
However, increased clock speeds following improvements in the access speed of memory cards in recent years has meant that it is no longer possible for the aforementioned delay amount to be prescribed with a fixed value. Thus, UHS-I (Ultra High Speed-1), which is a high-speed standard for SD memory cards, defines the need to adjust the data latch timing in the case of using a clock that is faster than a predetermined value. The operation of adjusting the latch timing is called tuning, and is generally performed when a memory card is mounted. Such tuning processing is described in Japanese Patent Laid-Open No. 2010-157058.
Also, in recent years, communication apparatuses that communicate with an external device using a wireless communication module that supports SDIO standards have appeared. Such communication apparatuses are able to stream HD quality moving image data using the wireless communication module that supports SDIO standards. Since the HD quality moving image data has a large data amount, the communication apparatus may need to transfer data in accordance with the UHS-I standard.
Even if the data latch timing, that is, the delay amount of the clock, is adjusted through tuning, this delay amount varies due to external factors such as subsequent changes in temperature. Thus, if tuning is only performed when a card is mounted or before the start of streaming, there is a possibility that the delay amount could change following a change in temperature during streaming and lead to data reception failure. On the other hand, since data cannot be transmitted or received during tuning, performing tuning during streaming could possibly result in a reduction in the transfer rate and loss of data.